A track roller assembly and a reduction gear apparatus of a construction machine are equipped with ferrous floating seal for the purpose of preventing leakage of a lubrication oil from inside thereof as well as entering of earth and sand therein. Accordingly, such floating seal devices are widely produced by applying adequate treatment in which a seal sliding surface thereof is quenched to have a hard martensite structure, or a large amount of hard cementite and Cr7C3 carbide of 30% by volume are crystallized while causing a parent phase to a martensite by quenching, in order to improve seizing resistance and abrasion resistance. Such an exemplary floating seal device is made by using a Ni-hard cast iron or a high-carbon and high-Cr cast iron (for example, as shown in Japanese Parent Publication (KOKAI) NO. S51-59007).
In addition, a ferrous floating seal device in which abrasion-resistant material is splayed to a seal sliding surface thereof is sometime used for some purposes.
In the ferrous floating seal used for sealing a lubricating oil in the reduction gears and the lower track rollers, a seal sliding surface thereof is abraded as fine particles of earth and sand are entered on the seal sliding surface by hulling motion in the earth and sand, and is lubed with the sealed lubrication oil therein. Accordingly, even in a case of a most conventionally used hard ferrous floating seal device made of a high-carbon and high-Cr cast iron excellent in abrasion resistance and seizing resistance, when setting pressure (press force) at assembling is high, considerable quenching crack (heat crack), seizing and abnormal abrasion occur on the seal sliding surface, resulting in leakage of oil.
And, even if various tool steels such as a cold work tool steel and a high speed steel (SKH material) are applied so as to increase the seizing resistance and the abrasion resistance, seizing due to defect of seizing resistance easily occurs, resulting in insufficient heat crack resistance and abrasion resistance. In addition, such steels are so expensive that a material costs would increase in view of material yields before a product is finished.
Furthermore, in resent years, construction machines such as bulldozer are required to be driven at a high speed for improvement in working efficiency, and therefore, the ferrous floating seal device necessarily rotates at a high speed. This also causes quenching crack, seizing and abnormal abrasion, resulting in leakage of oil.
In order to solve the above-mentioned problem, an object of the present invention is to provide a ferrous abrasion resistant sliding material and a ferrous abrasion resistant sliding member having improved seizing resistance, abrasion resistance and heat crack resistance.